Vanilla producers on the tropical island of Madagascar say a cyclone that killed 78 people has also damaged around 30 per cent of the crop in the world's biggest producer.
The valuable beans are often kept under armed guard after prices shot up from around $US20 ($A26) a kg in 2010 to around $US500 ($A661) a kg last year.
A US buyer supplying ingredients for supermarkets Trader Joe's, Whole Foods and coffee chain Starbucks said she expected prices to jump.
The flavouring is used in products from ice cream to coffee. Madagascar produces nearly half the world's crop, according the UN Food and Agriculture Administration.
Cyclone Enawo tore through the East African island last week. On Tuesday, authorities said the storm had killed 78 people, displaced nearly 250,000 and wounded 250.
"The destruction of uprooted fields and plants (means) losses are estimated at 30 per cent," said Mamy Razakarivony, president of the national vanilla exporters' group.
He said he feared higher prices would drive away buyers and that locals would sell immature vanilla pods damaged by the storm, introducing poor quality vanilla to the market. The harvest will not be ready until July.
Reuters data shows the price for black non-split Madagascar vanilla is currently at $US487.50 per kg. Black non-split vanilla from India is $US420 per kg, and from Papua New Guinea it is only $US210 per kg.
